Media access control for isochronous data packets in carrier sensing multiple access systems

Abstract

The present invention has solved the collision problems in a CSMA network protocol and at the same time optimized performance of the network. This is accomplished by giving control of the size of the reserved portion and the size of the reservation portion of the communication frame to stations in the network. Further, the reserved portion is allotted to isochronous data packets each of whose length is variable. Also, only those packets that have a reservation are in the frame, and they are placed in the frame in order in accordance with there position of the permission or reservation list. The network timing is controlled by one of the stations acting as a conductor for the network. This conductor station receives the reservation requests from the other stations and builds a beat packet. The beat packet is transmitted from the conductor station to all stations of the network, and provides the timing or beat of the network that all stations are synchronized with. In addition, the beat packet contains the permission list (reservation list) identifying the stations that will transmit, and when they will transmit during the frame. The network interrupt handler and the conductor at the conductor station build this beat packet.

What is claimed is: 
     
       1. In a communication network having a plurality of stations, media access control apparatus at the stations for controlling the transmission of isochronous data in communication frames on the network, the communication frames having a portion of the frame allocated to isochronous data packets, said media access control apparatus comprising: a conductor at one station building a timing packet for transmission to other stations, the timing packet containing a reservation list indicating the sequence of transmission of isochronous data packets in the frame;   a frame interrupt handler converting input data to isochronous data packets for transmission from the station and for converting isochronous data packets received from other stations into output data;   a counter responsive to the reservation list and generating an interrupt when an isochronous data packet at the station is to be scheduled for transmission; and   a network interrupt handler in response to the reservation list in the timing packet and the interrupt for scheduling an isochronous data packet for transmission by the station whereby the order of transmission onto the network of isochronous data packets by stations on the network is controlled to avoid collisions.   
     
     
       2. The media access control apparatus of claim 1 wherein said network interrupt handler operates with said counter to count a deferral value to generate the interrupt and thereby control transmission of an isochronous data packet by the station, said deferral value defining when other isochronous data packets in the communication frame are being transmitted on the network so that isochronous data packets from the plurality of stations do not collide. 
     
     
       3. The media access control apparatus of claim 2 further comprises: a detector detecting traffic on the network and generating a first signal; and   said counter generating the interrupt in response to counting a deferral value based on a position of a request in the reservation list and in response to the first signal.   
     
     
       4. The media access control apparatus of claim 1 and in addition synchronizing apparatus in each station for synchronizing synchronous input/output date at each station with network timing as defined by the timing packet, said synchronizing apparatus comprising: a local clock locked to a liming packet clock rate provided by the timing packet; and   said frame interrupt handler responsive to the local clock for converting synchronous input data synchronized with network timing to isochronous data packets for transmission from the station and for converting received isochronous data packets into synchronous output data synchronized with network timing.   
     
     
       5. The media access control apparatus of claim 4 wherein said network interrupt handler operates with said counter to count a deferral value to generate the interrupt and thereby control transmission of an isochronous data packet by the station, said deferral value defining when other isochronous data packets in the communication frame are being transmitted on the network so that isochronous data packets from plurality of stations do not collide. 
     
     
       6. The media access control apparatus of claim 5 further comprises: a detector detecting traffic on the network and generating a first signal; and   said counter generating the interrupt in response to counting a deferral value based on a position of a request in the reservation list and in response to the first signal.   
     
     
       7. In a communication network having a plurality of stations for transmitting and receiving communication frames, media access control apparatus at each station for controlling the transmission of isochronous data and asynchronous data in communication frames on the network, the communication frames having a portion of the frame allocated to isochronous data packets, a portion of the frame allocated to asynchronous data packets, and a timing packet said media access control apparatus in each station comprising: a frame interrupt handler converting input data to isochronous data packets for transmission from the station and for converting isochronous data packets received from other stations into output data;   said timing packet containing a reservation list indicating the sequence of transmission of a plurality of isochronous data packets in the frame;   a timer in response to the reservation list timing a first time interval and generating a first interrupt for an isochronous data packet to be transmitted by the station, said first time interval defining a scheduled time for transmission of the isochronous data packet from the station; and   a network interrupt handler in response to the first interrupt releasing an isochronous data packet for transmission by the station whereby the order of transmission onto the network of isochronous data packets by stations on the network is controlled to avoid collisions.   
     
     
       8. The media control apparatus of claim 7 and in addition: said timer in response to a second time interval generating a second interrupt when an asynchronous data packet is scheduled for transmission by the station, said second time interval defining a time when transmission of isochronous data packets in the communication frame has been completed; and   said network interrupt handler in response to the second interrupt releasing an asynchronous data packet for transmission by the station whereby the asynchronous data packet is transmission after transmission of isochronous data packets in the communication frame has been completed.   
     
     
       9. The media access control apparatus of claim 8 and in addition: said timer operates as an ordered persistent timer during the timing of said first time interval and said second time interval and operates as an adaptive persistent timer after the timing of said second time interval.   
     
     
       10. The media access control apparatus of claim 8 wherein said timer comprises: a detector detecting traffic on the network and generating a traffic signal;   a deferral interval timer generating the first interrupt in response to the traffic signal and in response to a deferral value based on a position of a request in a plurality of requests in the reservation list; and   said deferral interval timer generates the second interrupt in response to the traffic signal and in response to a deferral value based on a count indicative of the plurality of requests in the reservation list.   
     
     
       11. The media access control apparatus of 7 wherein said timer comprises: a detector detecting traffic on the network and generating a traffic signal; and   a deferral interval timer generating the first interrupt in response to the traffic signal and in response to a deferral value based on a position of a request in a plurality of requests in the reservation list.   
     
     
       12. In a communication network having a plurality of stations, a media control system for synchronizing input/output data of each station with network timing and for controlling the transmission of isochronous data and asynchronous data in communication frames on the network, the communication frames having a first portion of the frame allocated to isochronous data packets and a second portion of the frame allocated to asynchronous data packets, said system comprising: a conductor at a conductor station building one or more timing packets for transmission to other stations, the timing packets containing a reservation list indication the sequence of and the number of isochronous data packet transmission requests for the frame;   at least one station of said plurality of stations comprising: a frame interrupt handler for converging input data to isochronous data packets for transmission from the station and for converting received isochronous data packets into output data;   a supervisor converting control data into asynchronous data packets for transmission from the station and for converting received asynchronous data packets into output data;   a timer timing an active state of the network, an active state indicating a present transmission of one or more isochronous data packets on the network; and   a network interrupt handler operating with said timer and in response to the sequence of requests in the reservation list to control the sequence of transmission of isochronous data packet from the station with other isochronous data packets transmitted on the network and in response to the number of requests in the reservation list to control the transmission of asynchronous data packet from the station.     
     
     
       13. The system of claim 12 wherein said timer times a deferral time based on the sequence of requests in the reservation list to control transmission of a packet by said station so that isochronous data packets from the plurality of stations are transmitted in sequence and do not collide. 
     
     
       14. The system of claim 12 also synchronizing input/output data of each station with network timing and further comprising: said conductor station transmitting the timing packet at a clock rate of a local clock at the conductor station;   at least one station of said plurality of stations further comprising: a local clock locked to an arrival time of said timing packet; and   said frame interrupt handler responsive to the local clock converting synchronous input data synchronized with the local clock to isochronous data packets and for converting received isochronous data packets into synchronous output data synchronized with the local clock.     
     
     
       15. The system of claim 12 wherein said at least one station further comprises: a memory buffer coupled to said network interrupt handler and said frame interrupt handler for storing therebetween said isochronous data packets and said asynchronous data packets.   
     
     
       16. The system of claim 12, wherein said at least one station further comprises: a controller, coupled to said timer and said network interrupt handler, for controlling the transmission and receipt of said isochronous data packets and said asynchronous data packets of the network.   
     
     
       17. The system of claim 16, wherein said at least one station further comprises: a transceiver, coupled to said timer and said controller, for transmitting and receiving said isochronous data packets and said asynchronous data packets to and from the network.   
     
     
       18. In a communication network having a plurality of stations, media access control apparatus at each station for controlling the transmission and receipt of isochronous data and asynchronous data in communication frames on the network, the communication frames having a portion of the frame allocated to isochronous data packets and a portion of the frame allocated to asynchronous data packets, said media access control apparatus comprising: means for building a timing packet for transmission to the stations, the timing packet containing a reservation list indicating sequence of transmission of isochronous data packets in the frame;   detecting means for detecting an active state and an idle state of the network, the network being in the active state when a station is transmitting and being in the idle state when no station is transmitting;   deferral means for counting deferral values during the idle state and generating an interrupt to schedule transmission of a data packet by the station, said deferral values based on the reservation list in the timing packet; and   control means responsive to the interrupt for controlling the time of transmission of isochronous data packets and asynchronous data packets on said network whereby in a given frame isochronous data packets from a plurality of stations do not collide on the network and asynchronous data packets are transmitted to the extent there is space remaining in the frame.   
     
     
       19. The media access control apparatus of claim 18 wherein: said deferral means during the idle state counting a deferral value based on a position of a transmission request in the reservation list and generating an interrupt if counting of the deferral value is completed; and   said detecting means resetting said counting means to stop said counting means from generating the interrupt if said detecting means detects a change from the idle state to the active state during counting of the deferral value.   
     
     
       20. The media access control apparatus of claim 19 wherein: said control means in response to the interrupt initiates transmission of an isochronous data packet on the network whereby the isochronous data packet transmitted from the station does not collide with another isochronous data packet.   
     
     
       21. The media access control apparatus of claim 20 and in addition: said deferral means counting a deferral value during the active state and generating update interrupt when counting of a deferral value is completed; and   said control means in response to the update interrupt generating an updated deferral value for an isochronous data packet whose previous deferral value was not counted before said counting means was reset.   
     
     
       22. The media access control apparatus of claim 21 and in addition: said counting means during an idle state counting the updated deferral value and generating the interrupt if counting of said updated deferral value was completed before said detecting means detects the change to active state and resets said timer.   
     
     
       23. The media access control apparatus of claim 18 wherein the reservation list indicates the number of isochronous data packets in the frame, the deferral time interval for an isochronous data packet is based on a position of a transmission request in the reservation list, the deferral value for transmission of an asynchronous data packet is a deferral time interval based upon the number of isochronous data packets in the frame, and said deferral means comprises: an interval timing means for timing intervals in the active state and the idle state;   said interval timing means during the idle state timing a deferral time interval and generating an interrupt if the deferral time interval times out;   said interval timing means being reset before the deferral time interval times out if said detecting means indicates a transition to an active state during the deferral time interval.   
     
     
       24. The media access control apparatus of claim 23 and in addition: said control means in response to the interrupt initiates transmission of a data packet on the network.   
     
     
       25. The media access control apparatus of claim 24 and in addition: said interval timing means timing a predefined interval of time during the active state and generating an update interrupt when the predefined interval times out; and   said control means in response to the update interrupt generating an updated deferral time interval for a data packet whose previous deferral time interval did not time out before said timer was reset.   
     
     
       26. The media access control apparatus of claim 25 and in addition: said interval timing means during an idle state timing the updated deferral time interval and generating the interrupt if said updated deferral time interval times out before said detecting means detects the change to active state and resets said interval timing means.